//Node.cpp
Node::Node(DataType Item):item(Item)
{
lchild = 0;
rchild = 0;
}
DataType Node::getItem()
{
DataType anItem = item;
return anItem;
}
void Node::setItem( const DataType & data)
{
item = data;
}
Node* Node::getLChild() const
{
Node * p = lchild;
return p;
}
void Node::setLChild(Node * p)
{
lchild = p;
}
Node* Node::getRChild() const
{
Node * p = rchild;
return p;
}
void Node::setRChild(Node * p)
{
rchild = p;
}
Node::~Node()
{
}
//BST.cpp
DataType * BST::Search(const string name)
{
return Search(name, root);
}
DataType * BST::Search(const string name, Node * r)
{
if(r != 0)
{
if (name.compare(r->getItem().getname()) == 0)
return &(r->getItem());
else
{
if (name.compare(r->getItem().getname()) < 0)
return Search(name, r->getLChild());
else
return Search(name, r->getRChild());
}
}
else
return NULL;
}
//main.cpp
MyClass mc1("Tree","This is a tree");
MyClass mc2("Book","This is a book");
MyClass mc3("Zoo","This is a zoo");
BST tree;
tree.Insert(mc1);
tree.Insert(mc2);
tree.Insert(mc3);
MyClass * mc = tree.Search("Book");
if (mc != NULL)
cout << mc->getname() << endl;
The problem is at the MyClass object (mc) returned from Search function.
I trace into Search() and make sure "r->getItem()" get what I want.
anything wrong with "return &(r->getItem());" ?
Thanks!
++++++
I'm a little bit confused.. can I change to "DataType BST::Search(const string name)" instead of "DataType * BST::Search(const string name)"....it seems that the compiler cannot pass. the return NULL will have some problem...
but I try your method to change the DataType* Node::getIthem() it still have error....@@
I am guessing that Node::getItem()
returns a DataType
by value:
DataType Node::getItem();
When you take the address of that return value, you are essentially taking the address of something that will immediately disappear (a temporary). I suspect that Node
holds DataType
objects internally, in which case Node::getItem()
could return a pointer to one of these.
DataType* Node::getItem() { return &item; }
const DataType* Node::getItem() const { return &item; }
or return by reference:
DataType& Node::getItem() { return item; }
const DataType& Node::getItem() const { return item; }
return &(r->getItem());
will return the memory adress to whatever r->getItem()
returns, not the object itself. If r->getItem()
returns a pointer you will have to return (r->getItem());
.
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